1. Field of the Invention
The apparatus of the present invention relates to cassettes for x-ray films. More particularly, the present invention relates to a cassette holder for radiographic film material having magnetic components for adhering to the item being x-rayed.
2. General Background
In the field of radiographic photography, cassettes are widely used for holding the x-ray sensitive film. For example, in the medical field, film cassettes are used widely in conjunction with the x-ray machines found in hospitals and doctors' offices. Also, in the field of non-destructive testing, wherein welds between sections of pipe, or metal plates, must be x-rayed in order to determine if the weld is proper, or if there are other fissures in the metal, the x-ray film is very often loaded in a cassette so that it is in a light-free environment and is then placed on the item that is being x-rayed. It is imperative that the cassette placement be proper, and not be adjusted by field personnel during the exposure. In view of the fact that several types of radiation are encountered in industrial x-rays such as iridium 192, cobalt 60, it is imperative that the field personnel have little or no exposure to the x-ray process, and must be maintained in distance and shielded away from enduring the exposure to the ray.
Oftentimes, a problem is encountered in the industrial x-raying of cylindrical items, such as pipe welds and the like, wherein the cassette must be placed along a curvatured weld in order to determine if the weld is indeed free of flaws. Naturally, since the cassette cannot simply be placed on the item to be welded, there must be a means for adhering the cassette to the item, without the field personnel making contact at the time of exposure. At the present state of the art, the x-ray film is contained in a flexible cassette holder, which is able to adhere to the curved surface, and is normally held in place with the use of masking tape or the like around the item to be x-rayed. Oftentimes, problems are encountered with this particular method. For example, the masking tape can only be used a single time and disposed of which is very uneconomical. Should the masking tape or the like be wet, it will fail to hold and the object to be x-rayed must be dried in order to accomplish the x-ray. Therefore, this rather primitive means of adhering the cassette to the surface of the item to be welded is very unsatisfactory.
Several patents have been obtained in the art of cassettes for x-ray film, the most pertinent being as follows:
German Pat. DE-PS No. 1,112,887, relates to a cassette incorporating a sheet of elastic material which exerts magnetic contraction forces over its entire area for cooperating with an iron foil supported on the bottom of the cassette. This particular cassette is disadvantageous in that the very thin foil, which serves as a medium to which x-rays enter the internal space of a cassette, has a thermal expansion coefficient differing from that of the components on which the foil is supported, and very often becomes detached from its support folds, especially under temperature variations.
U.S. Pat. No. 2,811,251 issued to S. Yerkovich entitled "Means For Holding Cassettes In X-Ray Spot Film Devices" relates to an apparatus for holding an article within an enclosure so that spot film devices can be utilized for rapidly making radiographs. This in no way relates to a magnetic means for maintaining the cassette in place.
U.S. Pat. No. 3,499,147 issued to Goodman, et al, entitled "Cassette For Radiographic Film Material", relates to a cassette wherein a sandwich-type film holder combination with the cassette main frame is taught and adapted to compress the film holder into a light-tight structure when assembled.
U.S. Pat. No. 3,511,990 issued to Hauss entitled "Radiographic Film Cassette Having A Resilient Film Release Strip Therein" provides a film package or cassette having a pair of opposed interfaces. A layer of resilient material is disposed on at least one of the opposed faces and a strip of resilient material, having a greater thickness than the layer is provided along at least a portion of one edge of the layer of material so that the film contained is released from the resilient material.
U.S. Pat. No. 3,591,804 issued to Minasian entitled "Magnetically Attractive Marking Device And Holding Member For X-Ray Film Holder" relates to a film holder having markers for producing identifying images on the negative, with the markers having strips of magnetic material with identifying stencil letters cut therein. This particular patent does not, however, teach adhering of the cassette to the material to be x-rayed.
U.S. Pat. No. 3,704,369 issued to Paidosh entitled "X-Ray Film Cassette" teaches the use of an improved cassette for providing improved contact between the intensifying screen and the sensitized film.
U.S. Pat. No. 3,829,699 issued to Anspach, Jr. entitled "Holder For X-Ray Cassettes" teaches the use of a cassette holder for x-ray cassettes which can be made sterile and easily used in an operating room having means for sealing the inner side of the container cap to prevent contamination.
U.S. Pat. No. 3,971,470 issued to White entitled "X-Ray Cassette Film Holder" wherein the improvement is basically a means of providing the tray and the mating lid to be automatically urged into tight engagement when they are closed together.
U.S. Pat. No. 4,114,044 issued to Chiulli entitled "Radiographic Cassette Adapter" wherein is provided a means for allowing a large x-ray film cassette holder to be fitted with the adapter for allowing the use of smaller film so that various sizes of cassettes are not necessitated.
U.S. Pat. No. 4,313,538 issued to Bauer, et al, entitled "Film Cassette With An Opening For Exposing Data On A Film Accommodated Therein" provides a cassette particularly adapted with an enclosable opening through which data can be exposed onto a pre-determined portion of the film accommodated within an internal compartment of a cassette.
U.S. Pat. No. 4,331,236 issued to Bauer entitled "Container For X-Ray Film" having a first chamber for the film and a relatively narrow elongated second chamber for housing an elongated data carrier card, the two being separate and apart.
U.S. Pat. No. 4,350,248 issued to Bauer entitled "X-Ray Film Cassette With Magnetically Attracted Confining Plates" teaches the use of a cassette having two separate parts which are connected on one side by a hinge and which are connectable on the second end with a magnetic plate supported cassette wall and attracting a ferromagnetic foil for eliminating air inclusion between the intensifying shields and the x-ray film interposed therebetween. Although this patent does teach the use of a magnetic means within the cassette, it does not address the problem of the cassette being adhered to the object being x-rayed.
U.S. Pat. No. 4,346,300 issued to Turner entitled "Film Sheet Cassette" relates to a frame wherein a pressure plate between the front and back plate is held in operative position by the force of magnetic repulsion by an array of magnetic poles between the plates. Again, like the previous patent, this patent does use magnetic means within the cassette but not means for adapting the cassette to the item being x-rayed.